A harmonic signal may have a fundamental frequency and one or more overtones. Harmonic signals include, for example, speech and music. The fundamental frequency may be referred to as the first harmonic. A harmonic signal may include other harmonics that may occur at multiples of the first harmonic. For example, if the fundamental frequency is f at a certain time, then the other harmonics may have frequencies of 2f, 3f, and so forth.
The pitch of a harmonic signal is the frequency of the first harmonic. Because of the relationship between the harmonics, the pitch is also the distance in frequency between adjacent signals. For some harmonic signals, such as those with a low signal to noise ratio, the pitch of the harmonic signal may be difficult to estimate. For example, where the first harmonic of the signal is not visible, the pitch may be erroneously estimated as the frequency of the second harmonic, or twice the value of the actual pitch. Such an error may be referred to as an octave error.
The pitch of a harmonic signal may be used in a variety of applications. For example, for speech signals, the pitch may be used for speech recognition, signal reconstruction, and speaker recognition. Accordingly, techniques for accurately estimating the pitch of a harmonic signal may improve the performance of applications that use an estimated pitch.